A method for reducing free fatty acids in high acid value processed oils and fats by bioenzymatic method

Abstract

The present invention belongs to the field of oil processing, and more specifically, relates to a method for reducing free fatty acids in high acid value processed oils and fats based on a bio-enzymatic method. The present invention uses special lipase to esterify free fatty acids, tolerates the complex catalytic environment in different "processed oils and fats", and the esterification rate reaches more than 80%. After the esterification reaction, the acid value of the oil can be reduced to less than 10 mg / gKOH. While reducing the acid value, the fatty acid is converted into glyceride, which can be used directly as a raw material for preparing biodiesel, greatly increasing the yield and improving its added value. The present invention adds a pretreatment process before enzymatic esterification, and dehydrates and adsorbs and removes impurities according to different raw material characteristics to ensure that the enzymatic esterification is carried out efficiently. The acid removal process adopted by the present invention has a simpler operation process, completely abandons the need for high temperature conditions and the use of organic reagents, greatly reduces costs, improves efficiency, and achieves real cost reduction and efficiency improvement.

Description

Technical Field

[0001] The invention belongs to the field of oil processing, and more specifically, relates to a method for reducing free fatty acids in high-acid-value processed oils based on a bio-enzyme method. Background Art

[0002] China's biodiesel industry has faced some challenges in recent years, especially in exports.

[0003] In the domestic market, China's biodiesel production continues to grow, but the overall market vitality is suppressed by export restrictions. The estimated data for 2024 shows that although domestic demand remains stable, the overall growth of the industry may slow down due to sluggish exports.

[0004] In order to meet this challenge, the Chinese government and industry associations are actively seeking new export markets. "Processed oils and fats" with high acid values ​​include deodorized distillates (DD oils), palm fatty acid distillates (PFAD), slop oils, acidified oils and waste cooking oils, which are often used as raw materials for transesterification to prepare biodiesel. However, in order to meet the needs of foreign transesterification processes for preparing biodiesel, a large amount of free fatty acids in such oils and fats need to be removed. After reducing the acid value, "processed oils and fats" can be exported as raw materials for biodiesel, and the added value is greatly improved, which can serve as a new export market growth point. Therefore, it is particularly important to reduce costs and increase efficiency of the acid reduction process.

[0005] At present, the deacidification process of waste oil in factories mostly adopts high vacuum and high temperature distillation, that is, the boiling point difference between fatty acids and oils is used to heat the raw oil to 250°C under high vacuum to distill out the fatty acids, which consumes a lot of energy and makes the cost high. CN 202311789447.7 provides a method for extracting and removing fatty acids from waste oils using methanol. Although methanol is more environmentally friendly than other organic solvents, its recovery and refining process after evaporation still requires a certain amount of cost investment, which increases the complexity of the operation.

[0006] In recent years, the bioenzymatic method has gradually attracted people's attention because it can esterify free fatty acids in a relatively mild and highly selective manner without introducing unnecessary chemicals, while converting the fatty acids to be removed into usable glycerides. Narasimharao et al. (2007) believed that lipase has significant advantages in the field of esterification and acid reduction. It has high selectivity and can be carried out efficiently under mild conditions, avoiding the corrosion of traditional chemical catalysts to equipment and the environment. Ordinary lipases are difficult to maintain high catalytic activity in oils and fats with high acid values. It is usually necessary to use immobilized lipases, which can not only enable them to cope with complex catalytic environments, but also increase their reuse times, extend the service life of the enzyme, and reduce the cost of use.

[0007] In summary, the bioenzymatic method for reducing acid value is of great significance to the export status of biodiesel in my country. The present invention provides a method for reducing free fatty acids in high acid value processed oils and fats by bioenzymatic method, which greatly reduces costs, improves efficiency, and achieves real cost reduction and efficiency improvement. Summary of the invention

[0008] The purpose of the present invention is to remove toxins from vegetable oils using a green, environmentally friendly and efficient enzyme-catalyzed degradation method. To achieve the above-mentioned purpose, the present invention provides the following steps:

[0009] S1: Remove excess water from high acid value processed oil by dehydration, stir at 100℃-150℃ for 10min-60min and then seal and store;

[0010] S2: Add 2%-5% lipase and 5%-50% glycerol to the mass of the oil to the pretreated high acid value processed oil, heat at -0.098MPa-0.03MPa and 30℃-80℃ for 1-20h, separate the lipase and centrifuge to obtain low acid value and high added value processed oil.

[0011] The high acid value processed oils and fats include one or more of deodorized distillate (DD oil), palm fatty acid distillate (PFAD), hogwash oil, acidified oil and kitchen waste oil;

[0012] The dehydration method includes but is not limited to one or more of dehydration processes such as reduced pressure evaporation dehydration, ventilation evaporation dehydration, membrane separation dehydration and adsorption dehydration. Preferably, ventilation evaporation is used for dehydration, the gas is hot dry air, the evaporation temperature is 100°C-120°C, and the stirring time is 10min-60min.

[0013] When the high acid value processed oil is one or more of hogwash oil, acidified oil and kitchen waste oil, the high acid value processed oil after dehydration is further impurized, a certain amount of adsorbent is added, heated and stirred for a certain period of time, and the adsorbent is separated by centrifugation;

[0014] The lipase includes, but is not limited to, one or more lipases derived from Candida antarctica, Burkaholderia cepacia, and Thermomyces lanuginose.

[0015] The lipase includes but is not limited to one or more of lipase IM-NE100, lipase IM-NE04, lipase RIM-03, and lipase TL-IM;

[0016] The added amount is 1%-10%, preferably, the added amount is 2%-5% (w / w, compared to the mass of oil).

[0017] The amount of glycerol added is 5%-50% (w / w, compared to the mass of oil), the reaction temperature is 30°C-80°C, the reaction time is 1h-20h, and the vacuum degree is -0.098MPa-0.03MPa; preferably, the amount of glycerol added is 8%-30% (w / w, compared to the mass of oil), the reaction temperature is 50°C-70°C, the reaction time is 4h-8h, and the vacuum degree is -0.098MPa-0.06MPa.

[0018] The adsorbent includes but is not limited to one or more of bentonite, kaolin, activated carbon, molecular sieve and silica gel. Preferably, activated kaolin is used and the addition amount is 4%-12% (w / w, compared to the mass of oil).

[0019] The heating temperature is 100° C.-150° C., and the stirring time is 20 min-60 min. Preferably, the heating temperature is 110° C.-130° C., and the stirring time is 30 min-50 min.

[0020] The present invention uses special lipase to esterify free fatty acids, tolerates the complex catalytic environment in different "processed oils and fats", and the esterification rate reaches more than 80%. After the esterification reaction, the acid value of the oil can be reduced to less than 10 mg / g KOH. While reducing the acid value, the fatty acid is converted into glyceride, which can be directly used as a raw material for preparing biodiesel, greatly increasing the yield and improving its added value. The present invention adds a pretreatment process before enzymatic esterification, and dehydrates and adsorbs and removes impurities according to different raw material characteristics to ensure that the enzymatic esterification is carried out efficiently. The acid removal process adopted by the present invention has a simpler operating process, completely abandons the need for high temperature conditions and the use of organic reagents, greatly reduces costs, improves efficiency, and achieves real cost reduction and efficiency improvement. DETAILED DESCRIPTION

[0021] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The present invention can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0023] Example 1 Enzymatic esterification and acid reduction process of deodorized distillate (DD oil) and palm fatty acid distillate (PFAD)

[0024] There are fewer harmful impurities in deodorized distillate (DD oil) and palm fatty acid distillate (PFAD), and their effect on the activity of lipase is relatively weak, so no pretreatment for impurity removal is required.

[0025] The control group process is as follows:

[0026] The deodorized distillate (DD oil) with an acid value of 103 mg / g KOH was ventilated and evaporated to remove excess water at an evaporation temperature of 105°C and stirred for 50 minutes. Then 3% lipase was added, the mass ratio of oil to glycerol was 5:1, heated to 60°C, reacted at normal pressure for 6 hours, filtered to separate the lipase and centrifuged to remove the glycerol, and the acid value of the first reaction was 86.46 mg / g KOH.

[0027] The process of the experimental group is as follows:

[0028] Deodorized distillate (DD oil) and / or palm fatty acid distillate (PFAD) are respectively subjected to ventilation evaporation to remove excess water, and then a certain amount of lipase and glycerol are added, heated to 60°C, reacted under reduced pressure for 6 hours, and the lipase is filtered and separated and the glycerol is removed by centrifugation to obtain a processed oil with low acid value and high added value, and the acid value can reach below 10 mg / g KOH; the lipase is reused to carry out the above enzyme reaction.

[0029] Table 1 Process for enzymatic esterification and acid reduction of deodorized distillate (DD oil) and palm fatty acid distillate (PFAD)

[0030]

[0031] Example 2 Enzymatic esterification and acid reduction process of slop oil, acidified oil and kitchen waste oil

[0032] Sludge oil, acidified oil and waste cooking oil contain more harmful impurities, which have a relatively strong impact on the activity of lipase, and some impurities need to be removed in the pretreatment.

[0033] The control group process is as follows:

[0034] Compared with the case No. 5 in Example 2, in the waste cooking oil with an acid value of 158 mg / g KOH, the dehydrated oil was directly subjected to enzyme reaction, 3% lipase was added, the mass ratio of oil to glycerol was 5:1, heated to 60°C, reacted under reduced pressure for 6 hours, the lipase was separated by filtration and the glycerol was removed by centrifugation, and the acid value of the first reaction was 62.74 mg / gKOH.

[0035] The process of the experimental group is as follows:

[0036] The waste oil, acidified oil and kitchen waste oil are respectively ventilated and evaporated to remove excess water. The dehydrated oil is further impurized, a certain amount of white clay is added, heated and stirred for a certain time, and the adsorbent is separated by centrifugation. Then a certain amount of lipase and glycerol are added, heated to 60°C, reacted under reduced pressure for 6 hours, filtered to separate the lipase and centrifuged to remove the glycerol, and low acid value and high added value processed oil are obtained, and the acid value can reach below 15mg / g KOH; the lipase is reused to carry out the above enzyme reaction.

[0037] Table 2 Enzymatic esterification and acidification process of slop oil, acidified oil and kitchen waste oil

[0038]

[0039] The present invention uses special lipase to esterify free fatty acids, tolerates the complex catalytic environment in different "processed oils and fats", and the esterification rate reaches more than 80%. After the esterification reaction, the acid value of the oil can be reduced to less than 10 mg / g KOH. While reducing the acid value, the fatty acid is converted into glyceride, which can be directly used as a raw material for preparing biodiesel, greatly increasing the yield and improving its added value. The present invention adds a pretreatment process before enzymatic esterification, and dehydrates and adsorbs and removes impurities according to different raw material characteristics to ensure that the enzymatic esterification is carried out efficiently. The acid removal process adopted by the present invention has a simpler operating process, completely abandons the need for high temperature conditions and the use of organic reagents, greatly reduces costs, improves efficiency, and achieves real cost reduction and efficiency improvement.

Claims

1. A method for reducing free fatty acids in high acid value processed oils and fats by bioenzymatic method, characterized in that: The method comprises the following steps: S1: Remove excess water from high acid value processed oil by dehydration, stir at 100℃-150℃ for 10min-60min and then seal and store; S2: Add 2%-5% lipase and 5%-50% glycerol to the mass of the oil to the pretreated high acid value processed oil, heat at -0.098MPa-0.03MPa and 30℃-80℃ for 1-20h, separate the lipase and centrifuge to obtain low acid value and high added value processed oil.

2. The method according to claim 1, characterized in that In step S1, the high acid value processed oil is one or more of deodorized distillate (DD oil), palm fatty acid distillate (PFAD), slop oil, acidified oil and restaurant waste oil.

3. The method according to claim 1 or 2, characterized in that In step S1, the water removal method is one or more water removal processes such as reduced pressure evaporation water removal, ventilation evaporation water removal, membrane separation water removal and adsorption water removal.

4. The method according to claim 3, characterized in that In step S1, the water removal method is ventilation evaporation water removal, the ventilation gas is hot dry air, the evaporation temperature is 100°C-120°C, and the stirring time is 30min-50min.

5. The method according to any one of claims 1 to 4, characterized in that: In step S1, when the high acid value processed oil is one or more of slop oil, acidified oil and kitchen waste oil, an adsorbent is added at 4%-12% of the mass of the oil to further remove impurities.

6. The method according to claim 5, characterized in that The adsorbent is selected from one or more of bentonite, clay, activated carbon, molecular sieve and silica gel.

7. The method according to claim 5 or 6, characterized in that The adsorbent is white clay, and the addition amount is 4%-12% (w / w, compared to the mass of oil).

8. The method according to any one of claims 1 to 7, characterized in that: In step S2, the lipase includes, but is not limited to, one or more lipases derived from Candida antarctica, Burkaholderia cepacia, and Thermomyces lanuginose.

9. The method according to any one of claims 1 to 8, characterized in that: In step S2, the lipase includes, but is not limited to, one or more of lipase IM-NE100, lipase IM-NE04, lipase RIM-03, and lipase TL-IM.

10. The method according to any one of claims 1 to 9, characterized in that: In step S2, the amount of glycerol added is 8%-30%, the reaction temperature is 50°C-70°C, the reaction time is 4-8h, and the vacuum degree is -0.098MPa-0.06MPa.

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